I actually think the Union can take all of Europan North America. Canada is predominantly Anglophone (and probably somewhat sympathetic to the Union) as well as sparsely populated. California can easily be cut off from outside help thanks to Union sea power in the Pacific. Quebec is probably also not too terribly populated outside of a few key urban centers. Add in the fact that the Union has far more experience with industrialized warfare, is not a dependency of a horrifically overextended empire thousands of miles away, and has a great deal of men and resources to throw at the issue and the conclusion I come up with is.... not pretty if you're a Europan. It sure as hell won't be easy, and if the Union decides to bite off more than it can chew their might be a chance for the French to keep parts of Cali, but barring that I'd recommend the non-Inferior locals start reading up on Prophet Burr and learn how to sing Yankee Doodle in the proper key.
This.
I really don't see how the Union is supposed to lose here. I don't even see how it's supposed to be a close-run thing. Mega-France is an extremely powerful nation, but not powerful enough to outfight the RU (which has nearly all the territory and industry of OTL's USA) on North American soil, maintaining supply lines all the way across the Atlantic,
at the same time as waging a gigantic war in Europe against the Russians
and the Nordreich
and the British
and the rebellious Germans in the Confederation of the Rhine. (Aside: I definitely wouldn't want to be whoever's in charge of French logistics/war materiel provisions in TTL. They must be living in a horror movie, like a nightmare where you can never wake up.)
The one thing that makes me hesitant to reach this conclusion is that, if Custer (or—at a stretch, if he rises to power earlier than in Classic—Steele) conquers the rest of North America in
his time, that won't leave the author's favourite crazed American dictator, Charles Oswald, much left of his canonical role; with both the South
and the Europans in North America defeated, there wouldn't be much left for him to do. This pushes me towards the notion that the RU will play their good cards badly, and they'll find a way to snatch defeat from the jaws of victory—or, at least, get a weaker victory than they could and should be able to attain.
…but then again, I thought that in the Great American War, too. I didn't see how the divided Southron nations, with Carolina and Virginia as fierce enemies that I thought wouldn't be on the same side, were supposed to hold off Lincoln and the Union, and of course I knew that in Madness Classic they survived to the 20th century. As Redux had previously been so similar to (an expanded, more detailed version of) Classic, I doubted that
@Napoleon53 would really be willing to go for such a dramatic change to the plot-trajectory of the story as to let President Lincoln's Republican Union conquer the Southron nations. Well, I was
dramatically wrong.
So perhaps I should be afraid to underestimate the author's willingness to break from Classic and shatter our expectations!